Bug#799694: healpy: FTBFS on ppc64(el): No module named _tkinter

[Aaron M. Ucko]

Source: healpy
Version: 1.8.1-1
Severity: important
Justification: fails to build from source

Builds of healpy for ppc64 and ppc64el have been failing because
python-matplotlab tries to use the tkagg backend, which requires the
python-tk package.  A typical backtrace is

  self = <healpy.test.test_visufunc.TestNoCrash testMethod=test_cartview_ma_nocrash>
  
      def test_cartview_ma_nocrash(self):
  >       cartview(self.ma)
  
  healpy/test/test_visufunc.py:33: 
  _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 
  healpy/visufunc.py:482: in cartview
      import pylab
  /usr/lib/python2.7/dist-packages/pylab.py:1: in <module>
      from matplotlib.pylab import *
  /usr/lib/python2.7/dist-packages/matplotlib/pylab.py:274: in <module>
      from matplotlib.pyplot import *
  /usr/lib/python2.7/dist-packages/matplotlib/pyplot.py:109: in <module>
      _backend_mod, new_figure_manager, draw_if_interactive, _show = pylab_setup()
  /usr/lib/python2.7/dist-packages/matplotlib/backends/__init__.py:32: in pylab_setup
      globals(),locals(),[backend_name],0)
  /usr/lib/python2.7/dist-packages/matplotlib/backends/backend_tkagg.py:6: in <module>
      from six.moves import tkinter as Tk
  /usr/lib/python2.7/dist-packages/six.py:199: in load_module
      mod = mod._resolve()
  /usr/lib/python2.7/dist-packages/six.py:113: in _resolve
      return _import_module(self.mod)
  /usr/lib/python2.7/dist-packages/six.py:80: in _import_module
      __import__(name)
  _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 
  
      """
      
      __version__ = "$Revision: 81008 $"
      
      import sys
      if sys.platform == "win32":
          # Attempt to configure Tcl/Tk without requiring PATH
          import FixTk
      try:
          import _tkinter
      except ImportError, msg:
  >       raise ImportError, str(msg) + ', please install the python-tk package'
  E       ImportError: No module named _tkinter, please install the python-tk package
  
  /usr/lib/python2.7/lib-tk/Tkinter.py:42: ImportError

I'm not sure why this issue has only come up on those particular
architectures, so you might want to consider declaring an
unconditional build dependency on python-tk to be safe.

Anyway, please do take a look.

Thanks!